Trail Networks

Note - The details of the network algorithm are published in the
2004 JCDL conference proceedings. The paper is also available from TopoFusion and is
entitled Digital Trail Libraries (5 MB, pdf format).

If you are serious about GPS mapping you probably have amassed a large
collection of GPS tracks covering your favorite areas. Managing and
viewing a large number of tracks can be a big problem. Current
commercial mapping products are typically slowed to a crawl when displaying
large numbers of tracks. TopoFusion was designed for efficiency and is able
to display many tracks.

Even with a fast display speed, there is still the problem of
organizing and managing the tracks.
Typically you end up with dozens of tracks, each of which cover a
unique trail or two but ultimately end up duplicating ground covered
by other tracks. It is often difficult to remember which tracks cover
which specific trails.
TopoFusion offers a powerful method of managing track data.
It enables users to produce trail networks. A network of trails
consists of individual trail segments that link between trail
intersections. In a network, each trail covered by any track is only
represented once.

For example, here are three GPS tracks from different trips in the same area:

Overlaying the tracks yeilds:

Producing a network in TopoFusion gives:

The advantages of this approach are twofold:

First, instead of dealing with dozens of files with significant
overlap, a single file (the trail network) is produced that contains
one trail segment for each trail segment covered by the combination of
all tracks.

Second, where duplicate data is available, the tracks are averaged
together, producing a more accurate representation of the trail. The
more data collected on a trail, the better the representation. View detail image showing track
averaging (average is in cyan).

At last, recreational GPS track data can enjoy the accuracy of
differential GPS and other more advanced (and expensive) techniques!

With a network produced, additional features become available:

Trail intersections are marked and can be used as accurate waypoints.

Routes that were not represented by the any of the original data
can be created, mapped and measured. Trail segments can be combined
together to create a new route--possibly one you've never taken before.

Measurements on the trail segments will be more accurate due to the
track averaging.

Trail segments between intersection points can be elevation profiled
individually.

Imagine downloading a complete network of all trails in an area you
are about to visit. With TopoFusion you'll be able to view and
measure the details of each trail segment. You'll be able to come up
with your own way to visit the area instead of relying on others
suggested routes. The data you have will also be more accurate than
trail data from only single tracks!